Many forms of electronic color displays are currently available for the presentation of visual information. This visual information can include color information which is often created in various displays with the use of color filters. For example, liquid crystal displays (i.e. also known as LCD displays) typically include a layer of liquid crystal material disposed between two transparent electrodes. An electric field is applied to the electrodes to cause an alignment of the liquid crystal molecules to change, thereby altering a transmission characteristic of light emitted by the display. LCD displays typically employ color filters to produce colored information from light that is selectively transmitted by the display.
Organic light-emitting diodes (OLED) are a form of light emitting diodes (LED) which contain an emissive electroluminescent layer made up of organic materials. Displays incorporating OLED materials generally do not require a back-light illuminator, and therefore typically consume less power and are thinner than other types of displays such as LCD displays. OLED color displays can include different configurations. For example, in some configurations, the OLED materials directly emit colored light without necessarily requiring a passive color filter. In other configurations, a color filter is used in conjunction with a white OLED source to produce colored information.
Electrophoretic displays typically employ an electric field to cause a movement of charged particles to change a transmissive or reflective state of a pixel of the display. Unlike other conventional displays which employ a backlight to illuminate display pixels, electrophoretic displays mimic ordinary paper with their flexibility and their ability to reflect external light and thus are sometimes referred to as electronic paper or E-paper. Various electrophoretic displays can be controlled to maintain a given outputted image without drawing additional energy. Color information is displayed using various techniques including the use of colored charged particles or colored electrodes. Color filters have also been proposed for use with electrophoretic displays.
Color filters used in display panels typically include various patterns of color elements. Patterns of color filter elements can include patterns of red, green and/or blue color elements, for example. Color filters may be made with color elements of other colors. For example, color filters made up of cyan, magenta and yellow color elements are known. The color filter elements can be arranged in any of various suitable configurations. FIG. 1A shows a portion of a prior art “stripe configuration” color filter 10 having a plurality of red (R), green (G) and blue (B) color filter elements 12A, 12B and 12C respectively formed in alternating columns across a surface 13. As described herein, color filter elements such as color filter elements 12A, 12B and 12C are collectively referred to as color filter elements 12. In this case, color filter 10 corresponds to an LCD color filter which includes a color filter black matrix 15 (also referred to as matrix 15). Reflective displays such as electrophoretic displays need not include matrix 15. FIG. 1A shows that the various color filter elements 12 can be formed by elongated stripes that are subdivided by matrix cells 17 (also referred to as cells 17) into the individual color filter elements.
The stripe configuration shown in FIG. 1A illustrates one example configuration of color filter elements. Color filters may have other configurations. Mosaic configurations have color elements that alternate in both directions (e.g. along columns and rows) such that each color element resembles an “island”. Delta configurations (not-shown) have groups of different color elements arranged in a triangular relationship to each other. Mosaic and delta configurations are examples of “island” configurations. FIG. 1B shows a portion of a prior art color filter 10 arranged in a mosaic configuration in which color filter elements 12A, 12B and 12C are arranged in columns and alternate both across and along the columns. Whereas the illustrated examples described above show patterns of rectangular shaped color filter elements, patterns including elements made up of other shapes are also known. These shapes can include triangular or chevron shapes, for example.
Color filters can be formed by various methods on various substrates employed in associated displays. Conventional techniques include photolithographic processes, electrochemical processes, and printing process (e.g. inkjet printing), for example. Direct exposure processes (e.g. laser-induced thermal transfer processes) have also been proposed. In some manufacturing techniques, when laser-induced thermal transfer processes are used to produce a color filter, a color filter substrate also known as a receiver element is overlaid with a donor element that is then image-wise exposed to selectively transfer a colorant from the donor element to the receiver element. Preferred exposure methods use radiation beams such as laser beams to induce the transfer of the colorant to the receiver element. Diode lasers are particularly preferred for their low cost and small size.
Laser induced “thermal transfer” processes include: laser induced “dye transfer” processes, laser-induced “melt transfer” processes, laser-induced “ablation transfer” processes, and laser-induced “mass transfer” processes. Colorants transferred during laser-induced thermal transfer processes can include suitable dye-based or pigment-based compositions. Additional elements such as one or more binders may be transferred.
The final visual quality of a color display is highly dependant on maintaining a required alignment between the color filter elements and the pixel elements of the display (e.g. electrode structures or other active components) which control the activation of a display color pixel corresponding to a given color filter element. The achievement of this required alignment can be adversely affected by various factors. For example, although glass has been used as a common substrate material in various display components, there is an increased desire to employ alternate substrates such as plastics especially when factors such as increased flexibility and lower costs are further required of the display. When compared with glass, many plastics can undergo greater dimensional changes and distortions when exposed to varying environmental factors such as temperature and humidity. Additionally, or alternatively, plastic substrates may undergo dimensional changes and distortions under the influence of various processing steps used to form the displays. A required color filter alignment can therefore be difficult to achieve when it is desired that a patterned layer of color filter elements be aligned with, or be formed in alignment with a surface of a display assembly.
The material characteristics of various display substrates are not the only factors that can limit the final alignment of a color filter layer with a display assembly. For example, it can be difficult to visually align to the various display electrodes especially if the optical requirements of the display require the electrodes to be substantially transparent or colorless. Conversely, the relative opacity of various display elements can hinder the achievement of a desired color filter alignment. For example, a desired alignment between a color filter layer and various pixel electrodes of an electrophoretic display can be hindered by the opacity of the electrophoretic medium that is disposed between the two.
There remains a need for effective and practical methods and systems that facilitate a desired alignment between a patterned layer of color filter elements and other elements of a display assembly.
There remains a need for effective and practical methods and systems that facilitate the formation of a patterned layer of color filter elements onto a display assembly with a desired alignment with other elements of the display assembly.